1. Field of the Invention
The invention relates to an amplifier arrangement comprising a first amplifier having a first output terminal for the connection of a first terminal of a load and having at least a first power transistor with a main current path for carrying a first current, this current being related to a first load current flowing via the first output terminal, a second amplifier having a second output terminal for the connection of a second terminal of the load and having at least a second power transistor with a main current path for carrying a second current, this current being related to a second load current flowing via the second output terminal, first means for generating a first signal, this first signal being related to the first current, second means for generating a second signal, this second signal being related to the second current, third means for generating at least one control signal, this control signal being related to a sum of the first signal and the second signal, and protection means for limiting the first and the second load current depending upon the control signal.
Such an amplifier arrangement can be used in general for driving a load coupled between two amplifiers, the amplifiers being protected from supplying excessive load currents, and can be used in particular in car-radios, where short-circuits to a supply potential form an ever present hazard.
2. Description of the Related Art
Such an amplifier arrangement is known inter alia from European Patent Application 90201757.3. In the same way as the amplifier arrangement defined above, the amplifier arrangement described in said patent application generates the first and the second signal with the aid of first and second means, respectively, on the basis of the first and second signals third means generate the control signal, the control signal being used for controlling the protection means. In the event of a short-circuit, the protection means actuated by the control signal ensures that a drive applied to the power transistors is removed in order to prevent the power transistors from being overloaded as a result of the supply of a required short-circuit current. Nevertheless, in the case of, for example, a short-circuit from the first output terminal to a supply potential coupled to the collector of the second transistor, the first power transistor is forced to supply a required short-circuit current.
A disadvantage of such an amplifier arrangement is therefore that despite the removal of the drive, the power transistors have to deliver the required short-circuit current, as a result of which the power transistors may be overloaded.